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Claims and Abstract availability

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English Abstract

The present invention includes a method and apparatus for testing the integrity of a dialyzer (12) prior to use. The dialyzer (12) is tested in the same way as when used in the treatment of dialysis. The dialyzer (12) is primed in the normal manner. The arterial blood line (16) is clamped while the venous line (18) is vented to the atmosphere (44). The ultrafiltrate flow rate through dialyzer (12) is increased until a rate is achieved, so that blood passing through would be ultrafiltered. The dialyzer (12) is monitored for pressure increases. If the pressure does not increase the test fails.

Note: Claims are shown in the official language in which they were submitted.

CLAIMS:

1. A method for testing the integrity of a dialyzerseparating a dialysis chamber into a first side and a secondside, the first side being in fluid communication with anarterial line to carry fluid to the dialyzer and a venous lineto carry fluid from the dialyzer, comprising: applying adifferential pressure across the dialyzer; allowing air toenter at least one of said lines; and testing the differentialpressure across the dialyzer to determine whether there areleaks through the dialyzer from the first side to the secondside.

2. The method of claim 1, further comprising introducinga liquid into the arterial line and venous line whereby thedifferential pressure across the dialyzer transmits said liquidthrough the dialyzer from said first side to said second side.

3. The method of claim 2, wherein said liquid is asaline solution.

4. The method of claim 3, wherein said step of allowingair to enter is by venting the line to the atmosphere.

5. The method of claim 4, wherein the venous line andarterial line are in fluid communication with a dialysispatient, and further comprising interrupting the fluidcommunication between the arterial line and the patient.

7. The method of claim 5, wherein said step ofintroducing a liquid includes priming the first side of thedialyzer.

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8. The method of claim 7, wherein the dialyzer is deemeddefective if the pressure across the dialyzer is less than300 mm/Hg.

9. The method of claim 6, further comprising removingthe clamping after determining that the dialyzer has sufficientintegrity so that the dialyzer, arterial line and venous lineare in position for performing dialysis on a patient.

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Note: Descriptions are shown in the official language in which they were submitted.

CA 02233198 1998-03-26 WO 97/11770 PCT/US96/15528 METHOD FOR TESTING UtALYZER INTEGRITY BEFORE USEr FIELD OF THE INVENTIONa Described herein is a method for the detectionof blood leaks on a diaiyzer prior to use. Morespecifically, a method and apparatus, using existingdialysis treatment equipment,-for automatically testing adialyzer membrane for material integrity leaks prior toreusing the dialyzer is disclosed. BACKGROUND OF THE INVENTION Hemodialysis is a form of treatment for chronickidney failure. With hemodialysis, the patient's blood ispurified outside the body in an artificial kidney calleda dialyzer. A dialyzer contains a blood compartment and adialysate compartment separated by a membrane. The totalsurface area of the membrane measures 1-2 square meters. During a hemodialysis treatment the patient's blood isallowed to flow on one side of the membrane and dialysisfluid on the other. At the beginning of the dialysistreatment, the waste product level in the blood is high,while the dialysis fluid contains no such products. Sincethe waste products are usually small dissolved substancesthey are able to move from the blood through the membraneand into the dialysis fluid. This movement continuesuntil there is an equal level of the substances on bothsides of the membrane. In order to remove excess water from the blood,it is necessary to create a pressure difference betweenthe blood side and the dialysis fluid side of themembrane. The process of creating this pressure betweenthe two sides of the membrane is called ultrafiltration._ SUBSTITUTE SHEET (RULE 26)

CA 02233198 1998-03-26- WO 97/11770 PCT/gJS96/15528Hemodialysis using disposable dialyzers becamean extensively used method for performing dialysis qtreatment. One example of a widely used dialyzer of thistype is the hollow fiber dialyzer, having a blood compartment composed of a bundle of hollow fibers and adialysate compartment formed by a sleeve surrounding thefiber bundle. Treatment using disposable dialyzers,however, may be plagued with extremely high costs. Efforts undertaken to reduce the costsassociated with dialysis treatment concluded thatdisposable, hollow fiber dialyzers may be reused providedthat they are adequately cleansed of bacterial, proteinand other particulate matter. It is readily understoodthat the cleansing process as well as usage of thedialyzer may cause damage to the dialyzer. The cleansed~dialyzer must be tested for leakage between the blood andthe dialysate compartment caused by broken fibers orbroken seals. The importance of ensuring the integrity of adialyzer prior to its use or reuse is readily understood.If there is an integrity leak in the membrane, one caneither infuse non sterile dialysate into the patient or lose blood into the dialysate stream depending on thepressure gradients in the dialyzer. As indicated by the prior art, special machinesfor preparing dialyzers for reuse have been developedwhich often include testing means for testing leakage anddialyzing capability. For example, U.S. Patent 4,846,970of Bertelsen et al. discloses a cross-flow membrane test ,unit. The device of this invention has a bottom cellbody, a top cell body and a pair of laterally spaced O-rings forming a seal in between. The bottom cell body is-a-- SUBSTITUTE SHEET (RULE 26)

CA 02233198 1998-03-26 WO 97/11770 PCT/US96/15528provided with a feed spacer cavity and the top cell body' is provided with a permeate carrier cavity.- A testsample of the membrane is placed on the machine, and theflow dynamics of~a full scale dialysis system aresimulated. U.S. Patents 4,444,596 and 4,444,597 of Gortezet al. disclose an automated method and apparatus forcleaning and disinfecting dialyzers prior to reuse,having multiple stations simultaneously capable ofcleaning a plurality of dialyzers. By using the separatemachine of this invention, the dialyzer, station cleaningthe dialyzer and the patient are identified and theidentifications are stored in memory. The cleaningprocedures are automatically machine sequenced, and thesequence is selectively controlled using test proceduresmeasuring indicia of dialyzer reusability. Testprocedures on the machine include a blood presence test,a pressure leakage test, and an ultrafiltration ratetest. U.S. Patent 4,449,392 of Huschke teaches adevice for testing sterile filters. The filter testingdevice of this invention includes a filter housing thathas an air inlet, outlet, and receives the filter. Aninlet line is connected to the air inlet. An inlet valvefor the inlet line is controlled to produce a continuousand evenly increasing air pressure therein, and anelectronic pressure sensor monitors the air pressuretherein. An electronic evaluating and control circuit hasa time switch, an adjustable threshold device and a peakpressure detector, and controls the inlet valve, a ventvalve connected to the inlet line, and a recordingmechanism. The air pressure in the inlet line isincreased until it reaches a preset pressure. The inlet-3- SUBSTITUTE SHEET (RULE 26)

CA 02233198 1998-03-26WO 97/11770 PCT/LTS96/15528valve is then closed for the time period set on the timeswitch. Thereafter, air is again supplied to the inletline until no further pressure increases are detected bythe peak pressure sensor.- 5 U.S. Patent 5,064,529 of Hirayama et al.discloses an apparatus for testing membrane filters. Themembrane filter testing apparatus of this invention usesa control circuit for increasing the pressure at the- 10 primary side of a membrane filter. The control circuit is- fixedly accommodated in a housing and wetted with a- liquid. The pressure at the primary side is increased bygas at a predetermined rate. The pressure at the primary- side is checked after the lapse of a predetermined period- 15 of time to see if it is within a specified range.- Although the prior art has made advances inways to reduce costs associated with dialysis treatmentby developing machines which test dialyzer integrity- 20 before reuse, the machines themselves are costly. An_ operator is needed to program the machine, place the- diaiyzer on the machine, evaluate the output, and performwhatever other maintenance functions the particular- machine requires.- 25 A further limitation for testing dialyzers in- this fashion is that the dialyzer is tested in anenvironment apart from the environment in which it is- used. Testing the dialyzer as part of the cleaning_ 30 process does not take into account that the cleaning or- preparation process itself may damage the membrane.- A desired method for testing membrane integrity- would test the dialyzer on the same machine and in the ,- 35 same environment in which the dialyzer is used. It would-4-SUBSTITUTE SHEET (RULE 26)

CA 02233198 1998-03-26 WO 97/11770 PCT/US96/15528test the integrity of the membrane just prior to thedialyzer being used, and would utilize existing equipmentcurrently used for hemodialysis treatment, thus beingcost efficient for the user. SUMMARY OF THE INVENTION The present invention provides a method andapparatus for testing the integrity of a dialyzer priorto its use. The method of this invention provides anadvantage over the prior art in that it can be performedin conjunction with existing hardware used in thetreatment of dialysis. No special machines, valves orpressurized gas is required. Although described in terms of testing theintegrity of a dialyzer prior to its reuse, it is readilyunderstood that the method of this invention can bepracticed on all dialyzers, not just reused dialyzers.

A further advantage of the method of the

present invention is that it may be performed just prior

to commencing dialysis treatment. Often, separate

machines, such as those found in the prior art, cleanse,

sterilize and test the dialyzer before its use and do not

take into account that the cleansing or moving process

may also cause damage to the dialyzer. Damage may still

occur even after the dialyzer has been tested and

determined to be functioning well.

The method of the present invention includes

the following general steps. First, the dialyzer is

primed in the normal manner. The blood side is primed

with a saline solution and the dialysate side is primed

with a saline solution. Once primed, the blood lines and

_5_ SUBSTITUTE SHEET (RULE 26)

CA 02233198 2001-07-05977774-13the saline lines are clamped. The veno,~s line is vented to theatmosphere through the venous pressure line transducerprotector which keeps the blood side stE~rility intact. Next, the ultrafiltrate flow rate is increased tomaximum. The blood side prime volume i;~ ultrafiltered throughthe membrane and eventually replaced by air which has enteredthe circuit via the transduced protector. The pressure on the dialysate side is then checked. Since air cannot pass through an intact membrane, as more airenters the blood compartment and less p:riming fluid isavailable to meet the demand of the ult:rafiltrate flow rate,the transmembrane pressure increases. '.therefore, if thetransmembrane pressure has increased, the membrane is intactand can be used for treatment. If, on i~he other hand, thepressure on the dialysate side has not increased, then air musthave passed through the memberane and the dialysate machinecannot increase the pressure since the loop is open to theatmosphere. In summary this invention seek to provide a methodfor testing the integrity of a dialyzer separating a dialysischamber into a first side and a second side, the first sidebeing in fluid communication with an arterial line to carryfluid to the dialyzer and a venous line to carry fluid from thedialyzer, comprising: applying a differential pressure acrossthe dialyzer; allowing air to enter at 7_east one of said lines;and testing the differential pressure across the dialyzer todetermine whether there are leaks through the dialyzer from thefirst side to the second side.6

CA 02233198 2001-07-0577774-13 BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a schematic representation showing thecomponents of hemodialysis delivery syst=em. FIG. 2 is a circuit diagram showing the preferredembodiment of the flow circuit of the invention. FIG. 3 is a graph showing an example of the pressuregradients of the dialysis circuit for a successful test.6a

CA 02233198 1998-03-26 WO 97/11770 PCT/US96/15528 FIG. 4 is a graph showing an example of thepressure gradients of the dialysis circuit f or anunsuccessful test. FIG. 5 is a flow chart showing the pref erredembodiment of the method of this invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS IO With reference to FIG. 1, it can readily beseen that the practice of the method of this inventionrequires no additional equipment, and may readily bepracticed using standard hemodialysis treatment equipmentprogrammed for the test procedure. The method of thepresent invention is performed using the followingapparatus: a dialysis controller 10, a dialyzer 12, andbloodlines (16 and 18). Generally, the controller 10 performs the basicfunction of regulating the flow rate, pressure andtemperature of the dialysate. Standard features ofcontrollers include a blood pump, heparin pump, an airdetector, a blood leak detector, a dialysate fluid pump,monitors for blood, dialysis fluid and ultraffiltration,plus alarm circuits and automatic shut off. The dialyzer 12 consists of a bloodcompartment, a dialysate compartment and a membrane whichseparates the two. The total surface area of the membranemeasures 1 to 2, square meters. The membrane is a thinfilm with thousands of small holes that allow water andsmall dissolved substances to pass through, but retainproteins and blood cells, which are too large to pass,, through the membrane. During dialysis ultraffi ltration,hydrostatic pressure is exerted across the dialyzer SUBSTITUTE SHEET (RULE 26)

CA 02233198 1998-03-26WO 97/11770 PCT/US96/15528membrane causing the removal of excess fluid from thebloodstream.- Dialysis bloodlines (16 and 18) function to connect the patient to the pump and dialyzer, providing a- reliable path for blood from and to the access site 14.An arterial bloodline 16 takes blood to the dialyzerwhile the venous bloodline 18 takes blood back to thepatient. Practice of the method of the present inventionis readily understood with reference to FIG. 2. The diaiyzer 12 is primed with saline in the normal wayit is primed before initiating hemodialysis treatment. Once primed, the arterial bloodline 16 is clamped withclamp 46. The venous bloodline 18 is vented to theatmosphere 44 through the venous pressure line transducer26. The venous pressure line transducer 26, which can be- seen with reference to FIG 1., keeps the sterility of theblood side of the dialyzer 12 intact. Resuming the discussion with FIG. 2, theultrafiltrate f low rate 22 is increased to a maximum of3000 ml/hr. At this point, the blood side prime volume isultrafiltered through the membrane. Since the venousbloodline 18 is vented to the atmosphere 44, air nowenters the circuit through the transducer protector 26and fills the blood side of the dialyzer 12 where theblood side prime had previously been. Once the blood side prime is gone, thetransmembrane pressure is checked. In an intact membrane,air cannot pass through the membrane, so as more airenters the blood compartment and less priming fluid isavailable to meet the demands of the ultrafiltrate flow_g_- SUBSTITUTE SHEET (RULE 26)

CA 02233198 1998-03-26 WO 97/11770 PCT/US96/15528rate, the transmembrane pressure increases to a value' greater than 300 mmHg.l If the~dialysate side pressure has increased,the integrity of the dialyzer is confirmed and thedialyzer may be reused for dialysis treatment. Thisresult can be seen with reference to FIG. 3. If thetransmembrane pressure has not increased, then it is mostprobable that the dialyzer has a material integrity leakand should not be used. This result is depicted by FIG. 4. In use, the method of this invention worksgenerally as follows, as depicted in FIG. 5: Whilebetween patients scheduled to receive dialysis treatment,a nurse or technician working at that particular stationprimes the blood side and the dialysate sides of thedialyzer as well as the attached lines with saline in thenormal manner. The nurse or technician then stops theblood side flow to the dialyzer. Next, the nurse ortechnician presses the test button on the machine toperform the test that will evaluate the integrity of thedialyzer. The venous pressure monitor line is removedfrom the machine. The transmembrane pressure is checkedby the machine's standard pressure control mechanisms. If the transmembrane pressure has increased, the nurse ortechnician knows that the dialyzer is able to be reused. If the pressure on the dialysate side has not increased,the test fails and the nurse or technician knows that thedialyzer can not be used for further treatment._g__ SUBSTITUTE SHEET (RULE 26)

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